[llvm-commits] Speeding up instruction selection

[Roman Levenstein]

Hi Evan,

2008/4/2, Evan Cheng <evan.cheng at apple.com>:
>
>  On Apr 2, 2008, at 1:57 AM, Roman Levenstein wrote:
>
>  > 2008/4/2, Evan Cheng <evan.cheng at apple.com>:
>  >>
>  >> On Apr 2, 2008, at 12:55 AM, Roman Levenstein wrote:
>  >>
>  >>> Hi Evan,
>  >>>
>  >>> 2008/4/1, Evan Cheng <evan.cheng at apple.com>:
>  >>>> Please hold off checking it in for a bit. llvm tot is having some
>  >>>> problems and I'd like to get to the bottom of it first.
>  >>>
>  >>> OK.
>  >>>
>  >>>> Also, the tie breaker is less than ideal. I think we need a tie-
>  >>>> breaker that is "the SUnit that's added to the queue is preferred".
>  >>>> That means it prefers nodes which are closer to the end of block.
>  >>>> What
>  >>>> do you think?
>  >>>
>  >>> Do you actually mean "the SUnit that's added to the queue LAST (or
>  >>> FIRST) is preferred"? I'll think about it.
>  >>
>  >>
>  >> Yep "first".  Basically, if all else being equal, let the node that's
>  >> ready first be scheduled first. We can add a order id to SUnit which
>  >> gets set when it's pushed into the ready queue. What do you think?
>  >
>  > Makes sense. The queue should have a global "current id" counter. Its
>  > current value is assigned to each node being inserted into the ready
>  > queue and then incremented. When the node is removed from the queue
>  > for any reason, its queue order id is reset. It should be rather easy
>  > to implement.

>  > BTW, do you really want this queue order id in the SUnit or in a
>  > separate array indexed by SUnit unique ids?
>
>
> It should be in SUnit since the sort functions don't have access to
>  ScheduleDAG members.

Please find and review the attached patch implementing:
 - a proper tie-breaker as discussed above.
 - and unmodified part for replacing the slow std::priority_queue by
std::set, as it I already did before.

What do you think?

-Roman
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